For obtaining biofuels from biomass it is necessary for bacteria and enzymes to attack the hemicellulose and cellulose thereof to transform them into bioethanol or biogas. Hemicellulose and cellulose are protected by lignin, a fiber enveloping them and preventing said biological attack. Therefore the first step for obtaining biofuel is to pretreat the biomass to break the lignin and to make the hemicellulose and cellulose accessible to the bacteria and enzymes.
It is known in the state of the art that treatment of organic material at a temperature comprised between 160-240° C. causes the hydrolysis of a significant part of the organic material, therefore a process for thermal pretreatment of organic wastes, wood, etc has been developed. In the case of obtaining biofuels which currently form an important alternative to fossil fuels, a pretreatment of the biomass to be used considerably increases the conversion to the same which is of great economic and industrial interest.
Various processes for the pretreatment of biomass which are classified into chemical and thermal pretreatments are known, among which the process of vapor explosion which can be carried out in a conventional flash tank must be highlighted. In this sense WO96/09882 describes a pretreatment of biomass to break the lignin, based on the thermal explosion which consists of subjecting the biomass to heating and high pressure for suddenly releasing the pressure whereby the water retained inside the biomass explodes, breaking the lignin barrier and releasing the hemicellulose and cellulose on which bacteria and enzymes can then act. However, among other drawbacks, this process is not a continuous process and only around 50% of the invested energy is recovered in the process for pretreatment whereby the resulting energy balance is poor and the energy consumption needed to produce bioethanol or biogas is high.
Therefore and due to the increasing interest in biofuels, the need in the state of the art to provide an alternative process for the pretreatment of biomass which is efficient from an energy point of view and is therefore interesting to put it into practice at the industrial level continues to exist.